In order to establish electrical continuity between the brake, taillight and turn signal system of a towing vehicle and that of the towed vehicle it is necessary to install a relatively short wiring harness adjacent the rear bumper of the towing vehicle that makes the two systems compatible with one another and facilitates hook up. Typically, the harness is installed as an after-market item and is left on the towing vehicle permanently so that the vehicle is always electrically ready for hooking up to the trailer.
Since the wiring harness is permanently installed on the towing vehicle, it is desirable to have a neat, orderly installation which avoids loose, dangling wires which are not only unsightly but which can also snag on obstacles passing beneath the vehicle and can become contaminated with moisture, grit and grime. One way to encourage a clean, professional-looking installation is to take advantage of a small opening typically found in most truck bumpers in the vicinity of the ball hitch and license plate mounting bracket, such opening serving as an orifice through which the harness can be neatly threaded and thus held up out of the obstacles and contaminants below the vehicle.
However, such openings are typically smaller in diameter than the rubberized connectors at opposite ends of the harness. Thus, unless the opening is enlarged at the time of installing the harness, the opening cannot be used. This would necessitate drilling out the opening which not only increases installation time and necessitates more tools, but also may not be appreciated by the owner of the vehicle.